Sanjay Gupta, MD, Everyday Health: Harvey Brody is a good reminder for all of us of the damage that sun can do.

Harvey Brody: I was a mess. I had cancer all over me: my legs, my nose (obviously), my hands, even my head.

Dr. Gupta: Mr. Brody gets skin cancer as often as the rest of us get colds. There are three basic types of skin cancer, and he has had all of them. Basal cell carcinoma is the most common, but it is very rare that it travels to other parts of the body. Squamous cell carcinoma is a little bit more likely to metastasize, but still not gravely dangerous if it’s caught and treated.

Hooman Khorasani, MD, Chief, Division of Dermatologic and Cosmetic Surgery, Mount Sinai Hospital: And then you have the last one, which is melanoma. It's not the most common skin cancer, but it accounts for the most skin cancer-associated deaths in the U.S.

Dr. Gupta: So why does Mr. Brody get so many skin cancers? There are three factors that determine your risk: your lifetime sun exposure, your genetics, and your immune system, which is where Mr. Brody comes in.

First: sun. Your skin has a memory. Severe sunburns, even those in childhood, increase your risk.

Genetics. If you have blue eyes, pale skin, lots of freckles or moles, you’re at higher risk. If you have a family history or a personal history of skin cancer, you’re also at much higher risk.

Finally, your immune system. Your immune system is constantly destroying sun-damaged skin cells before they can grow into cancers. As we get older and our immune systems get weaker, we are more likely to get skin cancers.

Mr. Brody is virtually guaranteed of getting skin cancers, because he's taking drugs to suppress the immune system after a heart transplant in 2014.

Dr. Khorasani: He is a transplant patient. So all transplant patients tend to get skin cancers because they are on immunosuppressive medications.

Dr. Gupta: It didn’t help that Mr. Brody lived for years in Arizona. Since the transplant, he gets several skin cancers every year. But as long as he remains vigilant, Dr. Khorasani says they are not a threat.

Harvey Brody: I look for little bumps. I look for little pimples, something that doesn’t really heal the way it should really heal. And it's important that you look.

Dr. Gupta: In spite of our increased awareness of the dangers of the sun, skin cancer rates continue to climb. The number of people each year who get melanoma, the most dangerous skin cancer, has tripled since 1975.

So what do you look for? Well, there are five markers of a potential skin cancer, which you can remember by the first letters of the alphabet. So …

"A": asymmetry.

"B": border. If the border of a mole is irregular, that’s a warning sign.

C is an uneven color.

“D” is for diameter. Anything bigger than the end of your pinky finger should be watched.

And, most important, “E” is for evolving. Any mole that changes over time needs to be checked out.

Get a spouse or a friend to look at parts of your body you can’t see easily, including your back, the backs of your ears, and the top of your head under the hair.